These kind of tests require firing up a whole cluster of nodes, before the tests can actually be run. Compared to unit tests they are obviously way more time consuming, but the test infrastructure tries to minimize the time cost by only restarting the whole cluster, if this is configured explicitly.

The class your tests have to inherit from is ESIntegTestCase. By inheriting from this class, you will no longer need to start elasticsearch nodes manually in your test, although you might need to ensure that at least a certain number of nodes are up. The integration test behaviour can be configured heavily by specifying different system properties on test runs. See the TESTING.asciidoc documentation in the source repository for more information.

The number of shards used for indices created during integration tests is randomized between 1 and 10 unless overwritten upon index creation via index settings.
The rule of thumb is not to specify the number of shards unless needed, so that each test will use a different one all the time. Alternatively you can override the numberOfShards() method. The same applies to the numberOfReplicas() method.

The InternalTestCluster class is the heart of the cluster functionality in a randomized test and allows you to configure a specific setting or replay certain types of outages to check, how your custom code reacts.

ensureAtLeastNumNodes(n)

Ensure at least the specified number of nodes is running in the cluster

ensureAtMostNumNodes(n)

Ensure at most the specified number of nodes is running in the cluster

In order to execute any actions, you have to use a client. You can use the ESIntegTestCase.client() method to get back a random client. This client can be a TransportClient or a NodeClient - and usually you do not need to care as long as the action gets executed. There are several more methods for client selection inside of the InternalTestCluster class, which can be accessed using the ESIntegTestCase.internalCluster() method.

By default the tests are run with unique cluster per test suite. Of course all indices and templates are deleted between each test. However, sometimes you need to start a new cluster for each test - for example, if you load a certain plugin, but you do not want to load it for every test.

You can use the @ClusterScope annotation at class level to configure this behaviour

The above sample configures the test to use a new cluster for each test method. The default scope is SUITE (one cluster for all
test methods in the test). The numDataNodes settings allows you to only start a certain number of data nodes, which can speed up test
execution, as starting a new node is a costly and time consuming operation and might not be needed for this test.

By default, the testing infrastructure will randomly start dedicated master nodes. If you want to disable dedicated masters
you can set supportsDedicatedMasters=false in a similar fashion to the numDataNodes setting. If dedicated master nodes are not used,
data nodes will be allowed to become masters as well.

As elasticsearch is using JUnit 4, using the @Before and @After annotations is not a problem. However you should keep in mind, that this does not have any effect in your cluster setup, as the cluster is already up and running when those methods are run. So in case you want to configure settings - like loading a plugin on node startup - before the node is actually running, you should overwrite the nodePlugins() method from the ESIntegTestCase class and return the plugin classes each node should load.